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Summer has arrived with a vengeance, so it's time to adjust our approach to lawn care. Over the last week or so, we've experienced severe heat and humidity without much rainfall. Under these conditions, cool-season turfgrasses tend to grow at a much slower rate because temperatures are outside the optimum range for food production. Yet plant metabolism continues, and the net result is that food reserves start to become depleted this time of year.
Most food reserves for cool-season grasses are stored in the roots, so one ill effect of this process is shrinking of the root system. This is why it is so important not to fertilize too late into the spring. Encouraging growth when the turf is not inclined to grow leads to increased metabolism and a more rapid depletion of the plant's valuable reserves . How do we best handle these kinds of conditions right now?
First and foremost, irrigation becomes much more important. In a similar article a couple of months ago, I mentioned that deep, infrequent irrigation is ideal when growth conditions are good. Under current conditions, we should consider moving to a lighter and more regular irrigation schedule. Watering no longer benefits the roots because, with the heat, roots will continue to decline whether we water deeply or not. A better strategy now is to water less at any one time but do so more often to minimize the onset of stress. This will help keep turf plants from getting "crispy" and assuming a pale, grayish hue, both classic signs of summer stress. Conservative watering at this time of year also helps with the onset of brown patch, which is now appearing in turf across Kansas.
Other heat management strategies are more consistent with spring and fall recommendations. While we don't need to mow as often, we should still keep mowing heights in the 3-4" range and mow often enough not to remove more than one-third of the leaf blade. Mowing short compounds the stress the turf is already experiencing and opens the door for more sun-loving weeds like crabgrass or bermuda, both of which thrive under these severe conditions. Remember, a little TLC can go a long way in keeping our lawns healthy until better conditions arrive this fall. (MF)
Yellow nutsedge is a relatively common problem in lawns, especially in wet years or in lawns with irrigation. Although it looks like a grass, it is actually a sedge. Unlike grasses, sedges have triangular stems and leaves that are three-ranked instead of two-ranked, which means the leaves come off the stems in three different directions. Yellow nutsedge is pale green to yellow in color and grows rapidly in the spring and early summer. Because of this rapid shoot growth, it extends above the rest of the lawn only a few days after mowing. This weed is a good indicator of poor drainage, but it can be introduced into well-drained sites through contaminated topsoil or nursery stock.
Nutsedge is difficult to control culturally because it produces numerous tubers which give rise to new plants. As with many weeds, nutsedge is less competitive in a dense, healthy lawn than in an open, poor one.
Contrary to what you sometimes hear, pulling the nutsedge by hand does not necessarily make the problem worse. You have to be persistent, but eventually the nutsedge will die out. If you are planning to treat with a herbicide, it would be better to leave the nutsedge plants undisturbed so that the herbicide can be maximally translocated to the roots, rhizomes, and tubers.
Chemically, several products are available. Manage has been available for a few years now and is very effective and safe on most turfgrasses. It is also the most expensive, but if an infestation is not too severe, one application should take care of the problem. The Manage label says to apply it after nutsedge has reached the three- to eight-leaf stage. Waiting until this growth stage apparently results in improved translocation of the active ingredient to the underground tubers and rhizomes.
Basagran (bentazon) and MSMA (monosodium acidmethanearsonate) can also be used, but they are less effective than Manage and often cause temporary discoloration of the desirable turfgrass. (WU)
We are starting to see samples of tomatoes with golden-yellow to yellow to pink to white spots on the fruit. This type of damage is often caused by stink bugs; the shield-shaped insects that emit a foul odor when disturbed. The stink bug injures the fruit by using its mouthparts to probe. Color development is affected wherever probing occurs resulting in the off color, cloudy spots. Heavy feeding may result in spots coalescing so the tomatoes have a golden color. If you look closely, you can see the pinprick-sized puncture wounds in the middle of the spots. Hard, whitish, callous tissue develops beneath the skin at the area of wounding. By the time the spots are noticed the stink bugs are often long gone making control impossible. Often gardeners never noticed the insects in the first place. But if puncture wounds are found, stink bugs are the cause. Stink bug damage does not directly limit the use of the tomatoes. Affected tomatoes are safe to consume. (WU)
Bearded iris are well adapted to Kansas and multiply quickly. After several years, the centers of the clumps tend to lose vigor with most of the flowering occurring toward the outside. Dividing iris every 3 to 5 years will help rejuvenate them and increase flowering. Iris may be divided from late July through August, but late July through early August is considered ideal.
Since iris clumps are fairly shallow, it is easy to dig up the entire clump. You will notice that the root system of the plant consists of thick rhizomes and smaller feeder roots. Use a sharp knife to cut the rhizomes apart so that each division consists of a fan of leaves and a section of rhizome. The best divisions are made from a double fan which consists of two small rhizomes attached to a larger one forming a Y-shaped division.
Each of these small rhizomes has a fan of leaves. The rhizomes that do not split produce single fans. The double fans are preferred because they produce more flowers the first year after planting. Single fans take a year to build up strength.
Rhizomes that show signs of damage due to iris borer or soft rot may be discarded. But you may want to physically remove borers from rhizomes and replant as long as the damage is not severe. Also, it is possible to treat for mild cases of soft rot by scraping out the affected tissue, allowing it to dry in the sun and dipping it in a 10 percent solution of household bleach. Make the bleach solution by mixing one part bleach with nine parts water. Rinse the treated rhizomes with water and allow them to dry before replanting.
Cut the leaves back by two thirds before replanting. Prepare the soil by removing weeds and fertilizing. Fertilize according to soil test recommendations or by applying a complete fertilizer, such as a 10-10-10, at the rate of 1 pound per 100 square feet. Mix the fertilizer into the soil to a depth of 6 inches. Be wary of using a complete fertilizer in areas that have been fertilized heavily in the past. We are seeing a growing number of soil tests showing phosphorus levels that are high enough to interfere with the uptake of other nutrients. In such cases, a fertilizer that has a much higher first number (nitrogen) than second (phosphorus) should be used.
Iris are commonly placed in a triangular pattern using three divisions spaced 10 to 12 inches apart. The fans should face out from the center of the triangle so that the clump doesn't quickly become crowded. (WU)
Contributors:
Ward Upham, Extension Associate; Matt Fagerness, Turfgrass
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